1. Field of the Invention
The present invention is in the field of metering rolls and more particularly rolls for metering ink or like fluids, such rolls being commonly referred to as anilox rolls.
2. The Prior Art
It is known to provide an ink metering or anilox roll comprising a cylindrical core having formed in the periphery thereof a multiplicity of spaced ink-capturing cells. When used in an anilox process, the roller functions to pick up ink from an ink source and to deposit on a subsequent printing roller or the like, discrete, separated areas of ink, the quantity deposited being desirably controlled within close tolerances as a result of the size, configuration and spacing of the cells. An example of an advanced form of anilox or ink metering roll is disclosed in U.S. Pat. No. 3,613,578, wherein the cells formed in the surface of the roll are especially configurated to achieve ink transfer in a precise manner, as more fully set forth in said patent.
It will be readily recognized that the formation of anilox rolls having high concentrations per lineal inch of precisely shaped ink metering cells is a costly procedure, which cost is nonetheless justified due to the improved quality of printing resulting from the use of the rollers. Such rollers typically are comprised of metallic materials plated to permit the same to resist the corrosive influences of the inks employed, and are subject to relatively rapid wear, requiring their frequent replacement. Once again, the cost inhering in replacement due to wear is justified by the quality of resultant printing.
In areas where high quality printing is not mandatory, such as the imprinting of paper bags, corrugated boxes or the like, it is nonetheless highly desirable that precise quantities of ink be metered onto the printing apparatus by the anilox roll.
While it is theoretically possible to utilize anilox rollers, such as described in the above noted patent, for non-critical applications, such as bag imprinting, etc. and achieve the desired precise metering effects, the high wear factor and consequent high cost of roller replacement do not, as a practical matter, justify their use.
Attempts have recently been made to provide a durable ink transfer roll for non-critical printing applications, the roll comprising a cylindrical metal core covering with ceramic material. While such coated rollers possess the necessary durability, they are incapable of metering quantities of fluid to the printing apparatus with the degree of repeatability and precision desired even in such rough printing applications as bag printing, etc.